Caching: implementation details

This section covers some details of the caching mechanism which are not discussed in the user guide. If you are developing a plugin and want to modify the caching behavior of your classes, we recommend you read this section first.

Disabling caching for WorkflowNode

As discussed in the user guide, nodes which can have RETURN links cannot be cached. This is enforced on two levels:

• The _cachable property is set to False in the aiida.orm.nodes.process.ProcessNode, and only re-enabled in aiida.orm.nodes.process.calculation.calcjob.CalcJobNode and CalcFunctionNode. This means that a WorkflowNode will not be cached.
• The _store_from_cache method, which is used to “clone” an existing node, will raise an error if the existing node has any RETURN links. This extra safe-guard prevents cases where a user might incorrectly override the _cachable property on a WorkflowNode subclass.